I've been collecting coins like all of us
(but rare/collectable coins too). Most on line catalogs and auctions are going to be way off on the coins true value. Even many local coin shops tend to low ball the prices (due to their high overhead). Best to go to one of your local coin shows in your area (I think your profile says you live in Virginia) Most big city's have coin shows several times a year. They are your best source for good info and you can shop the coins for free at the show. If you want to find out on-line, buy a copy of the current GreySheet.
https://www.greysheet.com/ They will show you accurate bid and ask prices for "accurately graded coins". If you really have a rare and/or higher value coin, you probably should have it graded by NGC or PCGS. Coins are graded on a scale of 0 to 70. A few grade points can make a huge difference in price of truly rare coins and opinions can vary widely (5 or more points) even among honest dealers. NGC and/or PCGS will settle any grading dispute.
If you are talking about US coins, look for the following "key coins" (although there are many more). Here are few that will bring you some bigger bucks in the higher grades. 1909S Indian Head Penny, 1909S VDB Lincoln Penny, 1938D 3 leg Buffalo Nickel, 1916D Mercury Dime, 1932D or S Washington Quarter and for some really big bucks, look for a 1893S Morgan Dollar in mint condition. (If you had a roll of 1893S Morgan dollars in MS65 or better condition, most people would say "just retire and forget about investing".)
Feel free to PM me if you have a "few" specific coins you'd like to get an idea of value. All's I need is the coin type, date, mint mark and an idea of condition.